Electrochemical cells, such as lithium cells, usually have an anode, a cathode, and a separator disposed therebetween. The separator serves to prevent mechanical contact between the anode and cathode.
In lithium ion cells the separator is usually configured in the form of a porous polymeric layer through which liquid electrolyte can penetrate and thereby transfer lithium ions.
In order to achieve a higher cell voltage, metallic lithium (Li−0) can also be used on an anode side in lithium cells. When an anode made of metallic lithium is used, however, dendrites of metallic lithium can form upon charging; these can damage the separator of the cell or in some cases even penetrate through it and destroy the cell.
In practice, graphite is usually used as an anode material in order to avoid the formation of dendrites. Graphite is a lithium intercalation material into which lithium metal atoms can be deposited. As compared with pure metallic lithium, however, graphite has a cell voltage that is 0.3 V lower (referred to anode masse), and an energy density that is lower by several factors.
German Patent No. DE 102 55 121 A1 relates to a separator having an asymmetrical pore structure for an electrochemical cell.
PCT Application No. WO 2004/021477 A1 relates to an ion-conducting battery separator for lithium batteries and to a method for the manufacture thereof, and to the use thereof.